1. Field of the Disclosure
The invention relates to a device and method for dynamically compensating length changes undergone by a jacket of fiber cable so as to control stresses upon a fiber within the jacket.
2. Prior Art Discussion
Optical fiber lasers are heavily used in a variety of industrial application. The link between a fiber laser and a work station is known as a delivery or process fiber cable whose length may widely vary depending on a given architecture of system. Present cable structures fall into several categories one of which is disclosed in detail hereinbelow.
FIG. 1 illustrates a cross sectional view of delivery fiber cable 10 used, for example, in high power fiber lasers capable of guiding a kW beam. The cable 10 is configured with an outer jacket 12 circumscribing a metal sleeve 14 so that the opposing circumferences of respective jacket 12 and sleeve 14 are in continuous contact with one another. Placed inside sleeve 14 is a plastic buffer 16 spaced radially inwards from sleeve 14 and surrounding, in turn, a silica fiber 18. The fiber 18 is dimensioned so as to radially move relative to buffer 16 and has opposite ends coupled to respective fiber laser and work station.
As a rule, optical fiber cables, constructed as cable 10, are required to be operated without damage to fiber 18 over a wide range of temperatures leading the length change of cable 10. Often in the field, tensile forces applied to opposite ends of cable 10 and environmental humidity variation also account for the length variation of cable 10. Plastics which are normally used for the manufacturing of jacket 12 have a relatively high temperature coefficient of expansion and contraction and a relatively low tensile strength. In contrast, fiber 18 is configured with a relatively low temperature coefficient. Since silica fiber 18 along with cladding and coating are all relatively fragile, the length variations of jacket 12 may lead to additional pulling, tensile or compressing forces applied the opposite ends of fiber 18. The resulting mechanical stresses may detrimentally affect the parameters of fiber 18 and, sometimes, completely destroy the fiber 18.
A need, therefore, exists for providing a system—dynamic length compensator—capable of minimizing stresses upon a fiber in the configuration of FIG. 1 regardless of whether a cable jacket expands or contracts.
A further need exists for providing a method for configuring a dynamic length compensator.